Colorado’s warm, dry, windy weather pattern, explained

These miles have already been rotated 3,000 miles away from Colorado. In the central Pacific, the sea surface temperatures remain cooler than normal – “La Niña” – the opposite of the more familiar “El Nino.” When the ocean temperatures are cooler than average in the Pacific Ocean, it changes the heat balance in the atmosphere above and that changes the pattern of the jet stream. The jet stream is the river of fast moving air that circles the globe, bending and twisting as it swirls around the world. The position of the jet stream determines the storm track over North America in general and Colorado in particular.

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Denver7 Chief Meteorologist Mike Nelson explains the warm, dry, windy weather pattern in Colorado.

For the past several months, the jet stream has been mostly blowing from the Pacific Northwest across the Northern Rockies and then over the East Coast. This pattern has brought a lot of wind to Colorado, but has kept the main storm track to our north. As a result, we get a lot of windy days, but not much snow or rain. During the daytime, the heating from the Sun creates rising columns of air from the Earth’s surface – we call them “thermals.” A good analogy is to think about how hot air balloon rises since the heated air is less dense. As that rises, it will gradually cool and become heavier and fall back toward the ground. If there is a strong jet stream overhead, this rising and sinking air helps to pull some of the momentum from the jet stream down toward the surface – I like to call it a “shove from above!” This helps create the strong and gusty winds we often experience during the day. At night, the ground cools and so does the air just above it. The cooler air settles close to the ground and the strongest winds diminish. Of course, its fast moving cold front can sweep through the state at night and sometimes keep those strong winds blowing.

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Denver7 Chief Meteorologist Mike Nelson explains the warm, dry, windy weather pattern in Colorado.

Since the fall of Colorado, we have been missing out on moisture for most of the spring. The entire drought in the western United States has been a problem for several years and in many areas farther west, for the last two decades. When the soil dries out, there is little moisture available for evaporation, followed by condensation of that moisture into clouds and rainfall. You might remember the old “Water Cycle” from grade school – evaporation, condensation, then precipitation. Right now, our water cycle is not working very well because it has been so dry for so long.

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Denver7 Chief Meteorologist Mike Nelson explains the warm, dry, windy weather pattern in Colorado.

The current long range forecast does not bode well for this summer. Conditions are expected to last longer than average and warmer than average for the next three months. Ironic that cooler water (La Niña) is helping to bring us a hotter and drier summer! The La Niña is also a phenomenon that goes through cycles and eventually the ocean temperatures will become warmer than average (El Niño). When this finally does happen, our weather may well shift to a wetter than average pattern, but right now, that’s not in the cards for the next 90 days at least.

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Denver7 Chief Meteorologist Mike Nelson explains the warm, dry, windy weather pattern in Colorado.

One more thing to remember is that the longer-term changes in our climate due to global warming. Our planet is getting warmer because we are rapidly changing the chemistry of the atmosphere from the burning of fossil fuels. When we burn coal, oil or natural gas, part of what comes out of the tailpipe or the smokestack is carbon dioxide (CO2). Each molecule of CO2 acts like a feather in a down comforter, trapping or re-directing heat that would otherwise escape into outer space. We have changed the amount of carbon dioxide from about 280 parts per million (ppm) to the beginning of the Industrial Revolution, to over 417 ppm as of today. Now 417 ppm Seems like a small amount of oxygen and nitrogen in our air, but small amounts do matter. The same concentration of carbon monoxide (417 ppm) would leave us unconscious and close to death. Carbon monoxide (CO) is poisonous, carbon dioxide is not, but CO2 is very effective at trapping heat.

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Denver7 Chief Meteorologist Mike Nelson explains the warm, dry, windy weather pattern in Colorado.

Scientists have proven that doubling of the CO2 increases the heat retention of the atmosphere by 4.7 watts per square meter. The vastness of the Earth’s surface, it is an enormous amount of heat! The forcing from that increases in heat, will cause the average global temperature to warm by about 5 degrees Fahrenheit. Our planet has already been warmed by the beginning of the Industrial Revolution. The result is that there has been more drought, longer wildfire seasons, sea level rise from melting glaciers and more intense tropical storms. Each one of these changes has been predicted for decades by climate scientists, and we are witnessing the results before our eyes.

MORE ON DENVER7 +: Colorado’s changing climate: A special Earth Day presentation

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Denver7 Chief Meteorologist Mike Nelson explains the warm, dry, windy weather pattern in Colorado.

The key to sliding global warming is to stop lighting fossil carbon (coal, oil and natural gas) on fire. The great resources of fossil carbon were below the surface of the Earth over the past 300 million years. What took nature 3 million centuries to put in the ground, we have dug up and burned in less than three centuries. Fossil fuel has been a modern miracle – life without it would be cold, dark and short. But the scientific fact is that the increase in atmospheric carbon dioxide is trapping heat and warming the world. We can power our planet using other resources – obviously wind and solar, but there are others, such as hydro power and nuclear power. While each has its own set of issues, we can develop the technologies to minimize the problems. We have the knowledge, what we need is the will to do it.

“When it is asked, what will it cost to protect our environment, one more question should be asked. What will it cost our civilization, if we don’t? ” – Gaylord Nelson, Founder of Earth Day

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